Character mistake: In the beginning scene where the shuttle lands on Pandora, as Jake gets on his wheelchair preparing to alight from the shuttle, the man behind him unloading equipment has his exopack mask loose even though he is exposed to Pandora's atmosphere. (00:05:20)
Continuity mistake: When Jake is recording his first video log entry, he moves the recording camera around a little to get a better view of his face, and is looking directly at a screen to his right to see if he's centered his face correctly. In the very next shot, he is staring straight forward at the camera. (00:10:10)
Continuity mistake: In the scene where Parker is shown playing golf on the indoor golf course in RDA, the first time he hits the ball, there are two other balls lying on the course side by side. In the next shot, two are distant apart and in the shot after that, they are in their original position. (00:12:15)
Continuity mistake: When Selfridge is on the indoor putting green and says "Grace, you know, I enjoy our little talks", a woman walks behind him. A few seconds later the same woman walks behind him again, in the same direction. (00:12:40)
Continuity mistake: When Selfridge shows Grace the unobtainium ore, he picks it up with his left hand. In the next shot we can briefly see him passing the ore from his right hand into his left hand. The ore magically changed hands between the shots. (00:13:45)
Continuity mistake: During Jake's first video log, Dr. Spellman and Dr. Patel are leaning on a table. When the camera changes and Jake turns his head over his shoulder to ask the two doctors a question, Dr. Patel is much more leaned over than before the camera change. (00:13:48)
Continuity mistake: At approximately 15 mins and 15 seconds, Max is looking over the image and info on the activity for the Avatar drivers. When Jake first drives, he is wearing a black "dog tag" with a blue spot. When he walks over toward the viewing window with the portable screen at approximately 15 mins 30 seconds, the "dog tag" is orange with a spot of black. (00:15:15)
Continuity mistake: When Jake is trying to catch up with Neytiri, they get ambushed by Tsu'tey and his posse. Jake pulls out his dagger, but then throws it down to save his butt. He's surrounded. So he has his arms out where they can see it. While Neytiri is confronting Tsu'tey, Jake is in the background with his arms spread out, and his dagger back in the holder. (00:42:10)
Continuity mistake: In the scene shortly after Neytiri saves Jakes life in their first encounter and Neytiri knocks Jake down she is holding her bow with arrows. When the shot changes the arrows are gone, and when the shot changes again they are back. (00:44:00)
Continuity mistake: In the scene where Jake wakes up from his link and Grace asks him, "Is the avatar safe?" and he replies, "Yeah Doc, and you are not gonna believe where I am," her hand is on top of his shoulder. But as the camera angle changes back and forth her hand switches to the side of his upper arm and back to the shoulder without time to have made the move. (00:48:55)
Continuity mistake: In the scene after Jake was just in his avatar for the first time, he and the Colonel are discussing things around a holographic 3D map. With each shot, Jake's arms change from being straight out holding the edge of the table, to clasped in front of him, with no time to move the position in between. (00:49:30)
Continuity mistake: In the scene where Neytiri is showing Seze to Jake, Neytiri's ponytail changes positions between shots twice. She puts it over her left shoulder as Seze is landing, it's at her back in the next shot of her, then when she says "Ikran is not horse" it's over her shoulder again. (00:58:15)
Continuity mistake: (Extended Edition) In the scene we see Tsu'tey badly injured on the ground, he asks Jake to finish him off in the "Navi way". Tsu'tey reaches out for Jake's dagger and Jake assists him in taking the dagger out of the scabbard. In the next shot the dagger is back in Jake's scabbard and a moment later in the third shot the dagger is now out of the scabbard and in Jake's hand. (01:07:05)
Continuity mistake: In the scene where Grace is talking about the Tree of Souls in the mobile lab, Trudy stands behind Jake with her right hand on her hip and left hand hanging down. After grace says "Outsiders are strictly forbidden," we are shown a close-up shot of Jake and hear Grace continue with "You lucky swine." In the background, we see that Trudy has suddenly turned 90 degrees clockwise and is apparently supporting herself with her left arm on what seems to be the same table Norm is sitting on. (01:12:00)
Continuity mistake: In the scene where Neytiri and Jake are standing under the Tree of Voices and Neytiri says to Jake, "This is a place for prayers to be heard", Neytiri's queue is at her back. In the next shot it is hanging over her right shoulder. (01:18:45)
Continuity mistake: When Quaritch is scolding Jake for making out with a Na'vi, Jake moves his head to the right. In the immediate next angle, his head is straight. (01:31:25)
Continuity mistake: After Grace has been shot, when she and Jake are at the remote link-up site, Jake pulls a blanket up to Grace's shoulders, and the tip of it is still folded over. When the shot changes to a close-up of Grace, the blanket now lies completely flat. (01:52:30)
Continuity mistake: When Jake first gets into the "syncing" device and he says, "This is cool," Grace's hands are already on his leg. In the next shot she reaches for his legs, where he replies, "Don't, I got this."
Continuity mistake: AMP suit details such as the windshield wiper blade/arm as well as the grab handles on top of the cockpit appear and disappear throughout the film, depending on whether a CG model or practical prop are being used.
Continuity mistake: In a scene in the planning room (where the computer model of Pandora is being studied by Colonel Quaritch and Parker Selfridge), Jake is watching them move the model quickly to find something on it and they show his digital watch which says 2:19. Less than a minute later they show his watch again and it says 2:51.
Chosen answer: The Core didn't originate the name - it's been used since the 50's and even has its own Wikipedia article at http://en.wikipedia.org/wiki/Unobtainium. There it's described as "any fictional, extremely rare, costly, or impossible material, or (less commonly) device needed to fulfill a given design for a given application."
Jon Sandys ★